1. Technical Field
The present invention relates to an optical photographing lens system. More particularly, the present invention relates to a compact optical photographing lens system applicable to electronic products.
2. Description of Related Art
In recent years, with the popularity of mobile products with camera functionalities, the demand of miniaturized optical lens systems is increasing. The sensor of a conventional photographing camera is typically a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor) sensor. As the advanced semiconductor manufacturing technologies have allowed the pixel size of sensors to be reduced and compact optical lens systems have gradually evolved toward the field of higher megapixels, there is an increasing demand for compact optical lens systems featuring better image quality.
A conventional compact optical lens system employed in a portable electronic product mainly adopts a structure of four-element lens such as the one disclosed in U.S. Pat. No. 7,869,142. Due to the popularity of mobile products with high-end specifications, such as smart phones and PDAs (Personal Digital Assistants), the requirements for high resolution and image quality of modern compact optical lens systems has been increasing significantly. However, the conventional four-element lens structure cannot satisfy these requirements of the compact optical lens system.
For the traditional lens assembly technique, it is hard to achieve the compact size with more lenses and is unsuitable to apply on the compact and portable electronic product. In another conventional optical lens system with five-element lens such as the ones disclosed in U.S. Pat. No. 8,000,030, two lens elements which are closest to an object have positive refractive power and negative refractive power, respectively. However, the refractive power overly focuses to the lens element with positive refractive power, so that the spherical aberration is generated, and the telephoto functionality cannot be enhanced for reducing the back focal length and the total focal length of the optical lens system. Therefore, the high quality and compact optical lens system is hard to achieve.